As described in Non-patent Document 1, an absolute transmission rate control channel (E-AGCH: enhanced-absolute grant channel) is defined as a channel used by a radio base station in uplink enhancement to control a transmission rate of uplink user data (data to be transmitted through EDCH/E-DPDCH) from a mobile station.
Note that, in the uplink enhancement, the transmission rate of uplink user data is specified by factors such as: a transmission power ratio between an enhanced-dedicated physical data channel (E-DPDCH) used for the uplink user data and a dedicated physical control channel (DPCCH); a transmission power of the enhanced-dedicated physical data channel (E-DPDCH) used for the uplink user data; and a size of transmission data block of the uplink user data.
In the uplink enhancement, a radio base station maps, to the absolute transmission rate control channel, an absolute value of the allowable transmission rate of uplink user data from a mobile station. Then, the radio base station transmits the absolute value to each mobile station, so that the mobile station can determine the transmission rate of uplink user data based on the absolute value.
In the uplink enhancement, a radio base station generally means a cell in the radio base station if not otherwise specified. In addition, in the uplink enhancement, each mobile station UE is configured to receive an absolute transmission rate control channel (AGCH) from a serving cell of the mobile station UE.
Additionally, in the uplink enhancement, a transmission rate generally includes a size of a transport block and a transmission power ratio (ratio between the transmission power of E-DPDCH and the transmission power of DPDCH).
At this time, an effective period of the absolute transmission rate control channel (an effective period of an absolute value of the allowable transmission rate mapped to the absolute transmission rate control channel) is not particularly set, and the absolute value is valid until the reception of the next absolute transmission rate control channel.
Here, in the uplink enhancement, an effective period in general may be set according to a time elapsed since receiving the absolute transmission rate control channel (AGCH) (for example, 10 ms, 5 TTI (transmission time interval) or the like), or may be set in HARQ process units.
In an example shown in FIG. 13, HARQ processes #4 to #8 are set as an effective period of the absolute transmission rate control channel (AGCH).
For this reason, for example, when a radio base station desires a certain mobile station to stop transmitting uplink user data, the radio base station has to transmit another absolute transmission rate control channel such that the allowable transmission rate of the uplink user data of the mobile station can be set to “0 bps”, to thereby cause the mobile station to stop transmitting the uplink user data.
As a result, transmission power resource in the downlink is overspent, which leads to deterioration in radio capacity.
[Non-Patent Document 1] 3GPP TSG-RAN TS25.309 V6.2.0